Stabilization of fats and oils



2,397,976 STABEIZATION or FATS AND oms Daniel Keith OLeary, Mendenhali, Pa., assia'nor to E. 1. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application July 25, 1942, Serial No 452,359

1 -24Ciaims.

This invention relates'tc the stabilization of edible anini'ahvezetable, or fish oils, fats and 4 waxes, and more particularly to the stabilization ot-tatty glyce'ride's with thio-di-iatty acids. ;-It is well-known that vegetable, animal, and

fish oils, fats and waxes tend to'become rancid and discolor after storage. It isnot definitely 1 l nywn justrwhat causes the deterioration but it has been suggested that it may be due to oxidaftion orto the action of micro-organisms, to hydrolyticreactions caused by enzymes, or due to minute aniountsof impurities. Such deteriora- --"tion is highly objectionable and renders the fats a and oils unfit ior'manyu'ses;

" have been madeto overcome this deterioration,

Many attempts the addition of various substances to the fats been the aromatic amino compounds, halides such r cmooon cmomooon Carboxy undecyl-beta-thio-propionic acid i)n oH \CHzCHsCOOH Alpha-alpha-dithiodipropionlc acid S2[CH(CH3)COOH12 Beta-beta-dithicdipropionic acid S2( CH 2CH2COOH)2 The preferred. rancidity inhibitor of the invenand oils-havingbeen proposedto' inhibit or retardit. Among the suggested substances have videstabilized ediblezvegetable, animal, and fish .{Oi18,.f8its1 and waxes. Another object is topro vide compounds to be incorporated in fatty substanceslwhich. will retard orinhibittheir. deterijj oration and which are tree from the disadvanffjjtageous properties of compounds heretofore emplayed for this purpose. Still another object is to provide thio-di-i'atty acids such as beta-betathio-diprop'ionic 9.8 rancidity' inhibitors. other n w nd advantages of the invention will herexinaiter appear. v

These objects maybe accomplished in accord 'ance withthe invention by, stabilizing-edible 1 vegetable, animal, and flshoils, tats, and waxes against rancidity by; the use of thiOndl-IfittY acids,

' by which} mean compounds containing one.

or moresultur atoms eateries to two fatty acid groups. Examplesoi these acids a'retbio-dipropicnic acid, thio-dibutyric acid, thio divaleric acid, thio-distearie acid, thio-dlpalmitic acid, and

the higher thio-iatty-acids. The hydrogen atoms l or thealiphatic chain of these acids maybe substituted with hydrocarbons and particularly alkyl, alkoxy, or other groups which do not resultqarboxymethyl-beta-thio-propionic acid tion is beta-beta-thlo-dipropionlc acid,

5(CH2CH2COOH):

which is incorporated in the fat, wax, or oil in amounts ranging from 0.01 to 1.0% and generally speaking, the other compounds designated may be used on an equivalent molar weight basis.

The surprising and unexpected rancidity inhibitm efiect of the thio-poiycarboxylic acids is clearly demonstrated by the following tests. The tests were conducted by a method generally described as the Swift test, This method is described in "Oil and Soap," 10, 105409 (1933), in an article by A. E. King et al., An accelerated stability test using the peroxide value as an index." Briefly stated, this test involves placing the oil to be tested in a constant temperature bath and subsequently bubbling air through the oil. There follow results obtainedon the treatment of 'various oils with beta-beta-thio-dipropionic acid in the swift test. The peroxide value, as described in the above article is a measure 01 the degree of rancidity, each oil or fat having a fairl definite peroxide value at which it is definitely rancid.

1. Lord Hours aeration l Lard with peroxide value oi 20 or above is rancid.

2. Soy bean. oil

Pei-lords value Home Antioxidant aeration I This all with a peroxide value of was rancid.

1 This shortening with a peroxide value of 120 was rancid.

The diethyl, dioctyl and dilauryl esters of thiodipropionic acid have also been found to be excellenz antioxidants in various oils as shown by the Swift test. While they do not appear to be as effective on an equal weight basis, they are as effective on an equal sulfur content basis.

During the process of rancidification, oils and fats go through an induction period in which the peroxide value increases relatively slowly. After this induction period the peroxide value increases rapidly and the addition of antioxidants usually falls to have any effect. Thio asomrs The acid and its esters have shown excellent rancidity inhibiting properties when used in the manufacture of potato chips. Chips made with lard and stored at 40 C. became rancid at the I send or four days. It 0.1% of the acid is added foods, such, for example, as lard, lard oil, butter,

dicarboxylic acids and especially thlo dipropionic acid possesses the unusual property of reducing the peroxide value of oils if the acid is added before the end or the induction period. This property of th acid contributes to its man oncetiveness as an antioxidant. The lowering of the peroxide" value is accomplished by incorporating in the order of from 0.01 to 1.0% of the above rancidity inhibitors into the rancid product and then heating the resulting mixture to a temperature between 100 C. and 225 c. for from one to five hours.

The outstanding ability of thio dipropionic.

acid to reduce the peroxide value of oils which have started to go rancid is evident from th resuits of the following tests. test, cottonseed oil which 'had an original peroxide value of 24 was reduced to a peroxide value of 5 when heated to 99 C. for a few hours in the presence of 0.05% beta-beta-thio-dipropionic acid. Similarly soy bean .oil was reduced in peroxide value from 26 to 4 with similar heating in the presence of the acid.

A further decided advantage in the use of thio dipropionic acid and its esters is that they possess excellent rancidity inhibiting properties at both high and low temperatures. Other agents of this type often lack such properties at high temperatures, which prevents their use in applications calling for the cooking of fats,

, such as the manufacture of potato chips, doughnuts and the like. To demonstrate this thin films of lard were exposed in glass dishes at room temperature, 0., 70 0., and 90 C.

Thus in the Swift to the lard for cooking, the chips will not be- ]come rancid for 10 days. Chips made with cottonseed oil became rancid after 9 days, but when 0.1% of the acid was added 37 days were required for the, chips to become rancid.

These rancidity. inhibitors are exceptionally useful, because of their tasteless and odorless properties at the preferred concentration, in vegetable, animal, and fish oil fat-containing oleomargarlne, olive oil, cottonseed oil, co'rnoil, cod=liver oil, icecream, mayonnaise, salad dressings, as. well as products containing these materials such as pastry, cakes, crackers, cookies,

Th inhibitors may be added tothe material being treated in any suitable manner. They may,

for example, be mixed into the cold uniterial; 25

then added (in this way beta -beta thio dif propionic acid can be added with facility to fats,

the material may be heated and the'inhibitor oils, and waxes. for at C. the acid melts and is, therefore, easily dispersed lnthe molten state" into the material); or any other-suitable means may be' employed. It is not'necessary that the inhibior be miscible in the material treated'ior whether present, in the indicated amounts, as a solid I or as a liquid rancidity.

waxes or oil, they may. be sprayed, properly tected. This method of application isespecially adapted to the protection of meats, bacon,-salted nuts, shredded suet, Iattyfish, etc. 1 I

The inhibitors may likewise lie-used in ma sizing of paper, waxed paper or parchment paper to be used in the wrapping of fats, waxes, or oils,

where there is direct contact between the product and the wrapper. 'I claim:

against rancidity a member of the group c021 sisting Of edible vegetable, animal, and fish oils, fats, and waxes, by incorporating therein a compound selected. from the group consisting of thio di-iatty acids and their esters. g 2. A process which comprises protecting against rancidity a member of the group consisting of edible vegetable, animal, and flsholls, fats, and waxes, by incorporating therein a thio di-fatty acid. r I

3. A process which comprises protecting against rancidity a member of the group consisting of edible vegetable, animal, and fish oils,

di-fatty acid ester. 7 q I 4. A. process which comprises protecting against rancldity a member of the group consisting of edible vegetable, animal, and flshfloils,

bread, potato chips, doughnuts,"popcorn, and J thellke.

it nevertheless inhibits While the preferred methodof applying these inhibitors is by incorporating'them into'the tats,-

l. A process which comprises I protecting.

fats, and waxes, by incorporating therein a 'thio fats,'and waxes, by lncorporating therein bets.

process which comprises. protecting,

dilauryl ester of beta=beta-thi0-dipropionic acid.

'7. A process which comprises protecting against rancidity the oxygen-exposed surface of a member of the group.'consisting of edible vegetable, animal, and fish oils, fats, and waxes,.by the treatment or said surfaces with a thio di-fatty acid.

8. A process for the retarding of the rancidity f a member of the group consisting of edible vegetable, animal, and fish oils, fats, and Waxes, which comprises incorporating in the member of the group during the induction period a compound selected from the group consisting of thio di-fatty acids and their esters, and subsequently heating the resulting mixture.

9. A process for the retarding of the rancidity of a member of the'group consistingof edible vegetable, animal, and fish oils, fats, an waxes, which comprises incorporating beta-beta-thiodipropionic acid in the member of the group during the induction period and subsequently heating the resulting mixture.

10. A process for the retarding of the rancidity of a member of the group consisting of edible vegetable, animal, and fish oils, fats, and waxes, which comprises incorporating from 0.01 to 0.1%

vegetable, animal, and fish oils, fats, and waxes, fortified against rancidity by an ester of a thin di-fatty acid.

14. A member of the group consisting of edible vegetable, animal, and fish oils, fats and waxes,

fortified against rancidity by beta-beta-thimdipropionic acid.

15. A member of the group consisting of edible vegetable, animal, and fish oils, fats, and waxes, fortified against rancidity by a lauryl ester of beta-beta-thio-dipropionic acid.

16. A member of the group consisting of edible vegetable, animal, and fish oils, fats, and waxes, which has been fortified against rancidity by from 0.01 to 1.0% of a member of the group consisting of thin di-i'atiw acids and their esters.

17. A member of the group consisting of edible vegetable, animal, and fish oils, fats, and waxes, which has been fortified against rancidity by from 0.01 to 1.0% of beta-beta-thio dipropionic acid.

18. A fat containing food the fat content of which has been fortified against rancidity by a compound selected from the group consisting of thin di-fatty acids and their esters.

19. A fat containing food the fat content of which has been fortified against rancidity by a thin di-fatty acid.

20. A fat containing food the fat content of which has been fortified against rancidity by a beta-beta-thio-dipropionic acid.

beta-beta-thio-dipropionic acid in the member of I the group during the induction period and sub sequently heating the resulting mixture to a temli erature between 100 and 225 C.

11. A member of the group consisting of edible vegetable, animal, and fish oils, fats, and waxes,

stabilized against rancidity by a compound of the group consisting of thio di-fatty -acids and their esters.

12. A member of the group consisting oi edible Vegetable, animal, and fish oils, fats, and waxes,

fortified against rancidity by a thio (ii-fatty acid. 13. A member of the group consisting of edible 21. A fat containing food the fat content of which has been fortified against rancidity by from 0.01to 1.0% of a compound selected from the group consisting of thio di fatty acids and their esters.

22. Cottonseed oil fortified against rancidity by from 0.1 to 1.0% beta-beta-thio-dipropionic acid.

23. Lard oil fortified against rancldity by from 0.1 to 1.0% of the dilauryl ester of beta-betathio-dipropionic acid.

24. Lard fortified against ranciditr' by from 0.1 to 1.0% of beta-beta-thiodipropionic acid.

DANIEL KEITH OLEARY. 

